Tracer valves are well known in the machine tool field. Basically they comprise spool valves whose control position is responsive to the reaction between a stylus of the valve and a pattern or template. The pattern or template is related to a workpiece in which the profile of the pattern or template is to be duplicated by a cutting tool. The tracer valves control the operation of motors which cause appropriate machine movements to occur.
Tracer valves and their various modes of operation are fully described in Paul J. Weaver U.S. Pat. No. 3,186,425 issued June 1, 1965. This Weaver patent is incorporated herein in its entirety for its showing of tracer valve construction and operation, and for its showing of certain problems in the prior art.
Conventional tracer valves provide for control over one or more axes of motion of the machine tool. In one common variety, three dimensional tracing is enabled wherein three orthogonally related single axis spool valves are adjusted by the stylus so as to control operation of three motors which drive machine tool components along respective axes. The mode involved is called "3D" tracing. A sub-species of this type is two-axis control, and this mode is frequently called "360.degree." tracing. 360.degree. tracing can be accomplished with a 3D tracer valve by disabling one of its three valves.
Still another mode of tracing operation is called "coordinated" tracing, wherein one sector of a single spool valve controls bi-directional movement along one axis, and another sector of the valve controls the rate of motion along an axis perpendicular to the first axis. In this mode of tracing, when velocity increases along one axis it slows along the other.
These foregoing modes are fully described and discussed in the said Weaver patent, and also in Rosebrook U.S. Pat. Nos. 2,753,145 and 2,835,466 issued July 3, 1956 and May 20, 1958, respectively, which are also incorporated herein by reference for their showing of structural and functional parts of such valves.
It has long been an objective to be able to utilize a single valve construction for as many modes of tracing as possible. The said Weaver patent does provide optimim versatility in a hydraulic tracer valve. It enables 360.degree., 3D, and coordinated tracing to be accomplished with only one valve. However, this valve has not become popular, because when converting from 3D or 360.degree. tracing to coordinated tracing, or vice versa, it is necessary to make too many adjustments to parts of the valve. It is an object of this invention to improve upon the valve shown in the said Weaver patent, and to simplify the conversion procedure in such a way that the spool valves themselves do not have to be repositioned or adjusted. There results an optimum valve with simple multiple mode convertibility.
A valve according to this invention includes a first spool valve intended to be aligned along a vertical axis. The valve includes a body which supports a stylus. The stylus has a first ball-like member which mounts it for universal pivotal motion, that is to say, the stylus tip may swing in all directions from the axis of the stylus. This first ball-like member is mounted in a first ball seat so the entire stylus is vertically moveable along said axis. The stylus includes a second ball-like member to which is mounted a scotch yoke that transmits lateral movement to a pair of orthogonally oriented, horizontal spool valves which exert control along their respective axes. A transmission is carried at the top of the stylus. The transmission includes a ball which is seated in a conical recess in the top of the stylus. This ball is confronted by and supports the bottom of a spool of the vertically mounted first valve. This support is by way of a conical recess, or a flat conversion surface. The spool includes conventional external grooves and lands which cooperate with respective grooves and lands in an encircling sleeve to provide control for flow of hydraulic fluid to cause appropriate machine tool movements. The conical recess carried by the spool is mounted to a plunger, which enables it to be shifted axially relative to the conversion surface.
According to a preferred but optional feature of this invention, the spool and sleeve of said first spool valve includes grooves and lands respective to a first and a second control mode, as well as to a coordinating sector used with one of said modes.